This invention relates generally to liquid metering and transfer valves for use in a diluting system of the type wherein vessels, valves and connecting conduits are employed to measure, intermix, dilute and deliver fluids, particularly liquids, for the purpose of automatically making measurements and tests upon liquid samples for the medical, biological, chemical, industrial and allied fields.
In particular, the invention provides a multiposition fluid sampling, metering and delivery valve assembly operable with liquid and gaseous state fluids for delivering precise volumes of liquid samples and diluent respectively to pre-selected testing locations automatically without manual interaction and capable of being installed in a small, compact, stand-alone analyzer, said valve assembly capable of employing positive and/or negative pressure to move fluids therethrough in a reliable sequence, capable of performing the metering (measuring) of both sample and diluent within the valve assembly, said valve assembly further having means enabling self-cleaning and self-maintenance.
Apparatus of the general type with which the valve assembly of the herein invention is intended to operate employ the well known Coulter particle analyzing principle disclosed in U.S. Pat. No. 2,656,508 and are capable of many uses in the medical, biological, chemical and allied fields, in research as well as routine testing and requires means which can produce liquid mixtures of specific concentrations accurately and automatically. The analyzing apparatus is required to perform testing and measurements on a continuous basis with many tests made simultaneously and complex routines repeated with precision but with different samples. In such apparatus, the requisite liquid samples must be drawn and precisely measured, combined with preselected volumes of diluent to define the requisite dilutions and transferred to vessels within the apparatus for testing purposes. Often different degrees of dilution are required for determination of different parameters of the original sample. Sample quantities often are limited and hence the multiple operations and determinations preferably are performed utilizing a single liquid sample of relatively small volume and, accordingly, conservation of sample is a desired goal.
Accordingly, analytical apparatus of the type concerned are provided with diluting means incorporated as a part thereof for preparation and delivery to testing locations therewithin of sample suspensions of predetermined concentrations automatically and accurately, a major subsystem of said diluting means being a liquid metering and transfer valve assembly which includes internal segmenting passage means capable of being coupled to a source of liquid sample. A liquid sample is drawn along one path into said segmenting passage means and the valve assembly is operated to isolate a precise volume of said liquid sample from one internal path and place said precise volume into a second path. A desired volume of diluent is directed into the second path driving the measured precise volume of sample along with the diluent to deliver same to a testing vessel or station exterior of the valve assembly. Conventionally the source of said diluent is coupled to the valve assembly by suitable conduit means linked therebetween and driven by pump means and metering means provided within the apparatus.
Movement of the liquids is imparted by positive and/or negative pressure means effected by sources thereof coupled to the valve assembly and to said pump means and metering means. The apparatus includes myriad check valves and pinch valves required to control the flow of the various fluids within the apparatus. It would be desirable to provide a multifunctional metering and transfer valve assembly which would perform all measurement of the various liquids therewithin. The analyzing instrument desirably should be compact, highly reliable, modularly constructed at low cost particularly to provide for meeting the needs of physicians', veterinarians', clinical and alternative care testing requirements.
Preferably, the analyzing instrument should eliminate or at least minimize the interaction of the operator with the instrument, eliminating the necessity for manual dilutions, being capable of self-cleaning and self-maintaining, i.e. independent of the operator's intervention.
Thus, as mentioned, it becomes highly desirable to provide a sampling, metering and transfer valve assembly wherein all dilutions are provided by the valve assembly itself . . . all dilutions determined within the valve assembly, all volumetric metering of both sample and diluent effected within the valve assembly with means provided for backwashing and rinsing, including that of the coupling between the valve assembly and the sample source, that is, the aspirator probe through which the liquid sampled is drawn into the valve assembly. Thus a multiposition, multifunctional, stepwise programmably operable sampling, metering and transfer valve assembly which is capable of precise positioning on command, is desired.
Prior U.S. Pat. Nos., such as 3,567,390, 3,991,055, 4,152,391, 4,445,391, 4,507,977 and 4,702,889 provided examples of metering and transfer valve assemblies wherein internal measuring chambers, generally in the form of passageways, are provided.
The earliest of the above identified prior U.S. Pat. No. 3,567,390, provided a metering and transfer valve assembly having a pair of outer disc members and a central disc member sandwiched therebetween, its opposite surfaces frictionally engaged with the facing surface of the respective outer disc member. The discs are aligned axially and mounted on a spindle so that the outer discs are stationary while the center disc is rotatable between two positions. A pair of axially parallel segmenting passageway sets are provided in the central disc and matching passageways are provided so that in one position of the central disc, liquid sample is received within one segmenting passageway of one set. The central disc is rotated to a second position where a precise volume of the liquid sample is received within one segmenting passageway of one set. The central disc is rotated to a second position so as to subtend a precise volume of the liquid sample wihtin said one segmenting passageway and a known, externally metered volume of diluent is introduced into the valve assembly to sweep the subtended volume of liquid sample, along with said metered volume of diluent, to an exterior location for testing.
Simultaneous with the introduction of said liquid sample in the first position of the center valve disc, liquid is taken from said exterior location comprising a prior formed "first dilution" and transferred to one segmenting passageway of the second set. When the central disc is rotated to segment the precise volume of the liquid sample, the so-called "first dilution" also is segmented to provide a precise volume of the "first dilution" to form a "second dilution". Simultaneous with the delivery of the first mentioned dilution (liquid sample plus diluent) to said location exterior of the valve assembly, the segmented volume of the "first dilution" is swept from the one segmenting passageway of the second set along with a metered given volume of diluent to another exterior location where it constitutes a "second dilution". Note that the volumes of diluent are metered exterior of the valve assembly and delivered to the valve assembly. Additionally, the liquid sample is sequentially tested at said locations exterior of the valve assembly, the prior made "second dilution" being tested simultaneously with the testing of a current made "first dilution" . However, the basic principle underlying the instant invention is set forth in said U.S. Pat. No. 3,567,390 with the two sets of segmenting passageways being formed in the center or rotatable disc of the valve assembly.
U.S. Pat. No. 4,152,391 provides for the forming of three dilutions employing a single metering and transfer valve assembly comprising a pair of stationary disc members and a center, rotatable disc member sandwiched there between. The center disc carries one set of axially parallel segmenting passageways. The structure also includes a pair of external measuring loops secured to the central disc and passing through slots formed in one of the outer, stationary discs. The loops carry a precise volume of liquid sample and one of which is filled alternatively with the other simultaneously with introduction of the liquid sample into the segmenting passageway of said one set. As with the structure disclosed in U.S. Pat. No. 3,567,390, diluent is metered exterior of the valve assembly and introduced to the valve assembly. The loops are arranged in parallel, so that only one is filled with the liquid sample at the time liquid sample is introduced into the one of the said set of segmenting passageways. However, that one loop is arranged in series with said one of said set of segmenting passageways to enable a single aspiration (or drawing step) to fill same simultaneously although two separate loading steps are required to fill both loops, alternatively. The said valve structure also included gallery formations defining paths for communicating with selected passageways. Further, slot means were required to be formed in one of the outer disc members in order to permit passage of the loops enabling rotation of the central disc so as to effect the semgentation.
U.S. Pat. No. 4,445,391 provided a liquid metering and transfer valve assembly wherein a measuring loop was secured to one of the stationary outer discs in addition to the set of axially parallel segmenting passageways formed in the center disc. A series path thus was defined through the valve assembly so that a single loading stop sufficed to fill both loop and one axial passageway of the segmenting passageway set and, with rotation of the central disc, and introduction of diluent, both the segmented precise volume of sample in the segmenting passageway and in the loop was delivered simultaneously to a pair of different testing locations along with given volumes of diluent, the latter being metered and stored exterior of the valve assembly. This structure was less expensive to manufacture since galleries and slots were not required. However, only a pair of dilutions could be made. The loop had only one function, that is, to measure a precise volume of liquid sample, the same liquid sample introduced into the segmenting passageway set.
U.S. Pat. No. 4,507,977 was generally similar in construction to that disclosed in U.S. Pat. No. 4,445,391 but for the provision of means to enable mounting of an additional probe (or aspirator) means for introducing an additional liquid into the valve assembly. While the two liquid samples were capable of being operated upon by a single valve assembly, the samples had to be taken successively and the loop remained only functional to measure a second volume of the same liquid sample simultaneously introduced to the segmenting passageway set.
Commonly with the prior valve assembly constructions described, metering of the diluent at locations exterior of the valve, involved the provision of plural metering units, pumps, pinch and check valves, resulting in complex arrangements and requiring much interior space, reducing the compactness of the analyzing system. Very simply put, it would be highly desirable to provide means whereby all liquids, including diluent, could be metered within the valve assembly yet without increasing the complexity of the valve assembly.
An improvement of significance was made to the general liquid metering and transfer valve art when U.S. Pat. No. 4,702,889 provided means for obviating a problem of leakage experienced at the junctions of the various interior passageways formed in the valve discs comprising the valve assemblies. Leakage was encountered from said junctions, material travelling as by capillarity, along the frictionally engaged facing surfaces of said valve discs to foul the circumferential surfaces of said valve assemblage. In particular, the structure of said valve assembly was improved by providing means defining a continuous channel in one of the frictionally engaged facing surfaces of at least one stationary disc and the facing surface of the center disc member frictionally engaged therewith. The channel was provided to extend along the periphery of said one surface and had an inlet and an outlet defining a path independent of any of the internal passageways within the valve assembly and non-interferent therewith. The continuous channel disclosed in the U.S. Pat. No. 4,702,889 comprised an outer groove formed in one of the frictionally engaged surfaces extending along the outer periphery of the face of the disc in which it is formed substantially the circumferential extent of said disc and continuing at a location near the inner periphery of said face as an inner groove extending substantially the extent of the central axis passageway of the disc, the grooves being concentric with the central axial passageway, whereby to intercept any eluded material escaping from any of the junctions of the said passageways and travelling along the engaged surfaces toward the inner and/or outer circumferential surfaces of the valve assembly, preventing the migration thereof to said circumferential surfaces. The thus defined "cleaning grooves" were bridged by a groove portion formed therebetween and connecting the pair of concentric grooves. Diluent or rinsing fluid, peferably liquid, was introduced to the "cleaning channel" thus defined via the inlet thereto. The rinse liquid passed through the channel to wash any residue from the channel, but did not serve to clean the engaged opposing faces of said discs. Where a groove was formed in one face of one of said frictionally engaged pair of disc faces, an inlet and an outlet was provided for flushing that groove. The "cleaning channel" thus defined did not function to clean the engaged surfaces when rinse liquid was directed thereinto. The rinse liquid was injected for the purpose of flushing the channel of any residue which may have collected therein. In fact, disassembly remained a pre-requisite to cleaning of the frictionally engaged disc surfaces. It should be pointed out that there was no means available by which the frictionally engaged disc surfaces could be cleaned in the absence of disassembly.